Rotary Distributor for Pressure Multiplier

ABSTRACT

The invention provides a system for multiplying pressure comprising at least two hydraulic cylinders communicating with an exit supplying pressure, wherein each cylinder has a piston within a chamber; said pistons cooperating respectively with an associated piston to supply pressure at the exit; and a rotary distributor communicating with said both hydraulic cylinders, able to supply alternatively a fluid to each chamber for motion of the respected pistons and to ensure alternatively return of the pistons.

FIELD OF THE INVENTION

The present invention broadly relates to well injection for examplecementing. More particularly the invention relates to servicingapparatus for pumping fluids in downhole wells into a subterraneanreservoir, such as for instance an oil and/or gas reservoir or a waterreservoir.

DESCRIPTION OF THE PRIOR ART

When a cementing job is performed, pumping units are used to pump afluid downhole in the well. Usually high pressure pumps are needed toensure efficient pumping. To allow amplification of pressure, forexample pressure multiplier can be used. Pressure multipliers are wellknown in prior art. FIG. 1 shows a schematic representation of apressure multiplier. When piston 1A extends to the right at a constantspeed, piston 1B delivers a constant downstream flow of oil. At the sametime piston 1B is moving to the right, piston 2A retracts to the left inconjunction with piston 2B. When piston 1A reaches the right end of thecylinder, piston 2A reaches the left end of its cylinder. Piston 2A thenextends while piston 1A retracts. Pistons 1A and 2A have a surfacelarger than pistons 1B and 2B, in such a way that high pressure comesout of exit 4 when a relatively low pressure (compared to exit 4) comesin via the input 3. However such a pressure multiplier from prior arthas some drawback. The motion of the two pistons should produce aconstant and uniform flow output, but due to the change of directions ofpiston 1A and 2A, a dip is generated in the output flow at thedownstream of pistons 1B and 2B. Therefore, there is a need to improvethe pressure multiplier from prior art.

SUMMARY OF THE INVENTION

The invention discloses a system for multiplying pressure comprising atleast two hydraulic cylinders communicating with an exit supplyingpressure, wherein each cylinder has a piston within a chamber; saidpistons cooperating respectively with an associated piston to supplypressure at the exit; and a rotary distributor communicating with saidboth hydraulic cylinders, able to supply alternatively a fluid to eachchamber for motion of the respected pistons and to ensure alternativelyreturn of the pistons. In this way, the rotary distributor ensures analternative supply of the fluid into the chambers and also an exit ofthe fluid from the chambers.

Preferably, the rotary distributor is made of a mirror distributor plateable to rotate within a holder, wherein the position of the plate versusthe holder determines the supply of the fluid to one chamber and/or toanother. The mirror distributor plate rotates clockwise or invertedclockwise and each cycle of the system is determined by sequences inposition of the plate versus the holder. In a preferred embodiment, themirror distributor plate is made of, but not limited to, at least twoslots, the first slot ensuring supply of the fluid to each chamber andsecond slot ensuring return of the fluid from each chamber. By rotationof the plate, each cylinder is alternatively supplied by the fluid andemptied from the fluid, depending if the sequence is respectively acompression or a depression.

Preferably, the system is made of a first rod coupling first piston withthird associated piston; a second rod coupling second piston with fourthassociated piston; and a first free wheel connected to the first rod anda second free wheel connected to the second rod, said both free wheelscoupled with the rotary distributor such that motion of each pistonensures self rotation of the rotary distributor in one directionensuring alternative supply of each chamber with the fluid. Thisconfiguration allows a self driving of the rotary distributor.

In another embodiment, the rotary distributor is rotate by a step motor.In this way, the rotation is independent and controlled preferably witha micro-controller.

Preferably, a first sensor determining position of first or secondpiston in associated chamber is added. Advantageously, the systemcomprises two sensors; the first sensor determines position of firstpiston in first chamber and further comprising a second sensordetermining position of second piston in second chamber.

In another aspect of the invention a method for pumping an injectionfluid in a well using an apparatus above is disclosed. Preferably, theinjection fluid is but not limited to a cement slurry and the system isused in a cementing job. Other fluids can also be pumped, for variousapplications for example fracturing, stimulation or various welltreatments.

The system thanks to its little size can be used in environment whereplace is limited, for example offshore or on trucks.

Preferably, the system is used for multiplying pressure with a step ofpre-compression within each chamber of the cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments of the present invention can be understood with theappended drawings:

FIG. 1 shows a schematic diagram of a pressure multiplier from priorart.

FIG. 2 shows the apparatus according to the invention comprising arotary distributor valve.

FIG. 3A shows the rotary distributor in a first position.

FIG. 3B shows the rotary distributor in a second position, respectivelyturned from an angle of 180° compared to first position.

FIG. 4 shows the sequences of the apparatus according to the inventionduring function.

DETAILED DESCRIPTION

The present invention involves the use of a rotary distributor in thepistons assembly of prior art. FIG. 2 shows a schematic representationof the apparatus 10 according to the invention. A first piston 1A isconnected to a third piston 1B through a first rod 11. The first piston1A moves within a first chamber 10A and the third piston 1B moves withina third chamber 10B. The first piston 1A moves with a speed S1. Thissystem defines the first hydraulic cylinder. In the same way, a secondpiston 2A is connected to a fourth piston 2B through a second rod 22.The second piston 2A moves within a second chamber 20A and the fourthpiston 2B moves within a fourth chamber 20B. The second piston 2A moveswith a speed S2. This system defines the second hydraulic cylinder. Theposition of each piston can be known by using positioning sensors.Preferably, two position sensors are used for both first 1A and second2A piston; advantageously the sensors are magneto restrictivepositioning sensors which avoid contact. An exit 4 is located at the endof both cylinders and communicates with the third chamber 10B and thefourth chamber 20B. A rotary distributor 5 is coupled between the twocylinders. In this way, the hydraulic sequential valves are replaced bythis rotary distributor. Accordingly, the rotary distributor of theinvention is preferably a mirror distribution plate 5 within a holder 7.

The linear motion of each hydraulic rod (11, 22) is transformed to arotation motion that drives the rotary distributor 5 via a dual freewheel device (one for each cylinder). In this way, a first free wheel 6Ais connected to the first rod 11 and a second free wheel 6B is connectedto the second rod 22. The rotary distributor is placed between those twofree wheels (6A, 6B) and so always turns in the same rotation direction.Preferably, the rotary distributor is a rotary distributor built ofmirror distribution plate 5 containing two slots, first one to supplythe oil to the hydraulic cylinder chambers 5A and second one to ensurereturn of the cylinder to its initial position 5B. FIGS. 3A and 3B showthe rotary distributor 5 in more details and in function.

Alternatively, the rotary distributor can be rotated using a step motor(not shown on Figure). There are no free wheels and the rotarydistributor drives independently to ensure supply and return of oil intoand from the cylinders. Advantageously, the rotary distributor iscoupled with a micro-controller and displacement sensors to ensure aregular cycle of the apparatus 10. For example, two potentiometers onein each hydraulic cylinder will slave the step motor position.

FIG. 3A is a double view of the rotary distributor 5, at the right in alongitudinal view, at the left, in a transverse view according to theplan A-A. In following figures, the rotary distributor is described withtwo slots; however several slots can be used, especially if the pressureof the mirror distributor plate wants to be balanced. Advantageously,the slippers on each slot/orifice shall be equipped with de-pressurizinggrooves. The rotary distributor may also be built with multi stagesbecause of high flow-rate.

The first slot 5A supplies the oil to the hydraulic cylinder chambers toallow the motion in the pumping direction. A variable displacement pump8 (FIG. 2) only supplies the oil to the pumping direction chambers. Ateach end of the slot a progressive groove allows for a short period tosupply oil to both cylinder chambers. Due to constant oil flow in thesystem the sum of the linear speed of the rods is constant in this wayreducing the pulsation of the system to a minimum. The second slot 5Bensures the return of the cylinder to its initial position (suctiondirection). The return is ensured by a pressure/flow controlledhydraulic spring (not shown) allowing a good volumetric efficiency ofthe pumping system. For a short period of time (Short angle of therotary distributor) the pressure discharge is connected to bothhydraulic cylinders. This feature allows the process pumping system towork without spikes.

FIG. 3B is a double view of the rotary distributor 5, at the right in alongitudinal view, at the left, in a transverse view according to theplan A-A. Compared to FIG. 3A, FIG. 3B represents the mirror distributorplate turned from an angle of 180°. In this configuration supply of thesecond cylinder is ensured and return of the first one is allowed.

FIG. 4 is a diagram showing sequences of the function cycle of theapparatus 10 of the invention. Step A shows the first cylinder inpumping mode and the second cylinder in return mode, the first slot 5Aensures supply to extension of the first piston 1A in first cylinder andsecond slot 5B return of the second piston 2A in second cylinder. Step Bshows the first cylinder in pumping mode and the second cylinder inpre-compression mode, the first slot 5A ensures supply to extension ofthe first piston 1A in first cylinder and also to pre-compress thesecond piston 2A in second cylinder. Pre-compression ensures a betterefficiency of the apparatus 10. Step C shows the first cylinder inpumping mode and the second cylinder also in pumping mode, the firstslot 5A ensures both supply to extension of the first piston 1A in firstcylinder and the second piston 2A in second cylinder. Step D shows thefirst cylinder in return mode and the second cylinder in pumping mode,the first slot 5A ensures supply to extension of the second piston 2A insecond cylinder and second slot 5B return of the first piston 1A infirst cylinder. Step E shows the second cylinder in pumping mode and thefirst cylinder in pre-compression mode, the first slot 5A ensures supplyto extension of the second piston 2A in second cylinder and also topre-compress the first piston 1A in first cylinder. Step F shows thefirst cylinder in pumping mode and the second cylinder also in pumpingmode, the first slot 5A ensures both supply to extension of the firstpiston 1A in first cylinder and the second piston 2A in second cylinder.Step G shows the apparatus at the same stage at defined in step A, andcycle can continue.

1. A system [(10)] for multiplying pressure comprising: at least twohydraulic cylinders communicating with an exit [(4)] supplying pressure,wherein each cylinder has a piston within a chamber, said pistonscooperating respectively with an associated piston to supply pressure atthe exit [(4)]; and a rotary distributor [(5)] communicating with saidboth hydraulic cylinders, able to supply fluid alternatively to eachchamber to cause back and forth motion of said pistons.
 2. The system ofclaim 1, wherein [the] said rotary distributor comprises a mirrordistributor plate [(5)] able to rotate within a holder [(7)], whereinthe position of the plate [(5)] versus the holder [(7)] determines thefluid supply to each chamber.
 3. The system of claim 2, wherein [the]said mirror distributor plate [(5)] comprises at least two slots, thefirst slot [(5A)] ensuring fluid supply to each chamber and the secondslot (5B) ensuring fluid return from each chamber.
 4. The systemaccording to claim 1, further comprising: a first rod [(10A)] couplingthe first piston [(1A)] with the third associated piston [(1B)]; asecond rod [(10A)] coupling the second piston [(2A)] with the fourthassociated piston [(2B)]; and a first free wheel [(6A)] connected to thefirst rod and a second free wheel [(6B)] connected to the second rod,both free wheels coupled with the rotary distributor [(5)] such thatmotion of each piston ensures self rotation of the rotary distributor inone direction, ensuring alternative fluid supply [of] to each chamber.5. The system according to claim 1, wherein the rotary distributor isrotated by a step motor.
 6. The system according to claim 1, furthercomprising at least a first sensor for determining the position of thefirst or second piston in the associated chamber.
 7. The system of claim6, wherein the first sensor determines the position of the first piston[(1A)] in the first chamber, and further comprising a second sensor fordetermining the position of the second piston [(2A)] in the secondchamber.
 8. A method for pumping an injection fluid in a well using anapparatus according to claim
 1. 9. The method of claim 8, wherein theinjection fluid is cement slurry.
 10. The system according to claim 2,further comprising: a first rod coupling the first piston with the thirdassociated piston; a second rod coupling the second piston with thefourth associated piston; and a first free wheel connected to the firstrod and a second free wheel connected to the second rod, both freewheels coupled with the rotary distributor such that motion of eachpiston ensures self rotation of the rotary distributor in one direction,ensuring alternative fluid supply to each chamber.
 11. The systemaccording to claim 2, wherein said rotary distributor is rotated by astep motor.
 12. The system according to claim 2, further comprising atleast a first sensor for determining the position of the first or secondpiston in the associated chamber.
 13. The system of claim 12, whereinthe first sensor determines the position of the first piston in thefirst chamber, and further comprising a second sensor for determiningthe position of the second piston in the second chamber.
 14. A methodfor pumping an injection fluid in a well, using an apparatus accordingto claim
 2. 15. The method of claim 14, wherein the injection fluid iscement slurry.
 16. The system according to claim 3, further comprising:a first rod coupling the first piston with the third associated piston;a second rod coupling the second piston with the fourth associatedpiston; and a first free wheel connected to the first rod and a secondfree wheel connected to the second rod, both free wheels coupled withthe rotary distributor such that motion of each piston ensures selfrotation of the rotary distributor in one direction, ensuringalternative fluid supply to each chamber.
 17. The system according toclaim 3, wherein said rotary distributor is rotated by a step motor. 18.The system according to claim 3, further comprising at least a firstsensor for determining the position of the first or second piston in theassociated chamber.
 19. The system of claim 18, wherein the first sensordetermines the position of the first piston in the first chamber, andfurther comprising a second sensor for determining the position of thesecond piston in the second chamber.
 20. A method for pumping aninjection fluid in a well, using an apparatus according to claim
 3. 21.The method of claim 20, wherein the injection fluid is cement slurry.22. The system according to claim 4, further comprising at least a firstsensor for determining the position of the first or second piston in theassociated chamber.
 23. The system of claim 22, wherein the first sensordetermines the position of the first piston in the first chamber, andfurther comprising a second sensor for determining the position of thesecond piston in the second chamber.
 24. A method for pumping aninjection fluid in a well, using an apparatus according to claim
 4. 25.The method of claim 24, wherein the injection fluid is cement slurry.26. The system according to claim 5, further comprising at least a firstsensor for determining the position of the first or second piston in theassociated chamber.
 27. The system of claim 26, wherein the first sensordetermines the position of the first piston in the first chamber, andfurther comprising a second sensor for determining the position of thesecond piston in the second chamber.
 28. A method for pumping aninjection fluid in a well, using an apparatus according to claim
 5. 29.The method of claim 28, wherein the injection fluid is cement slurry.30. A method for pumping an injection fluid in a well, using anapparatus according to claim
 7. 31. The method of claim 30, wherein theinjection fluid is cement slurry.